In a motor, when a large magnet is directly mounted in a rotor, large eddy current loss is generated in the magnet by a magnetic flux. As a technique to reduce the eddy current loss, conventionally, a large magnet is cleaved or split once into a plurality of magnet parts, these cleaved magnet parts are assembled together again and mounted in a rotor. This can reduce the eddy current loss. In this case, a cleaved face is coated with resin to form a resistance layer to further reduce the eddy current loss.
On the other hand, Patent Document 1 discloses another technique that a straight linear recess is formed on the surface of a plate-shaped workpiece made of a magnetic material or a fragile material such as glass, not magnet, and, both sides of the plate-shaped workpiece are clamped and one side thereof is rotated, thereby cleaving the plate-shaped workpiece along the linear recess.